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2 Sheets- Sheet 2.

(No Model.)

0. s. FORBES. MAGNETIG TELEPHONE.

Patented 00t.. 11, 1892.

UNITED STATES PATENT OFFICE.

CHARLES STEWART FORBES, OF LONDON, ENGLAND.

MAGNETIC 'l'E LEPHONE.

SPECIFICATION forming part of Letters llatent No. 484,150, dated October 11 ,1892.

' Application filed May 16, 1892. Serial No. 433,181. (No model.)

To all whom item/my concern.-

Be it known. that I, CHARLES STEWART FORBES, baronet, residing at No. 28 Queens GateTerrace,London,England,have invented an Improved Magnetic Telephone, of which the following is a specification.

The object of my invention is to utilize more perfectly the magnets employed for ringing the alternate current-bells employed in telephone combinations for the purpose of transmitting speech, thus dispensing with the separate telephone-magnets employed for this purpose. I find by the particular arrangement of parts hereinafter described that I can obtain a very powerful instrument which will transmit speech over long distances as a simple telephone; but when combined with a microphone I obtain greatly-enhanced effects.

To enable my invention to be clearly understood, I will describe the same by the aid of the accompanying drawings, in which- Figure 1 is a part-sectional elevation of a combined telephone and magneto machine having one metallic tympan. Fig. 2 is a plan of same, the cover of case being removed. Fig. 3 is a general view. Fig. 4 is a front elevation of cylindrical telephone, the door of case being removed. Fig. 5 is a plan of same, the top of case being removed.- Fig. 6 is an enlarged sectional View of the cylinder shown in Fig. 4. Fig. 7 is a part sectional view of cylinder, showing alternative device for adjusting tympans. Fig. 8 is a plan, part in section, of narrow cylinder with double tympan. Fig. 9 is an enlargedview of T-shaped polar extension.

Referring to lid of the wooden or other box or case 1.

2 is a trumpet-shaped mouthpiece formed of any suitable material, such as wood, ebonite, or metal. This may be attached to the case 1 byscrews 3or by gluing or like means. Mounted upon the door of the case is a thin sheet of pine or other soft wood, and to this the microphone 5,when employed, is attached.

Secured to the case by bolts 6 are ringingmagnets constructed of suitable steel bars 8- say six inches long by three-fourths of an inch by three-eighths of an inch-and I find six such bars, three on either side, (see Fig. 4,) a convenient number to use 5 but more or the drawings, 1, Fig. 1, is the less may in some cases be employed with advantage, depending upon the effect required from the instrument. The lower end of these bars are fitted with cast or wrought iron polepieces 9, and within these revolves, when actuated by any ofthe well-known devicessuch as adisk 9, engaging with a suitable pinion.

' threaded thereon, which serves to clamp the polar extension 13 to the pole-piece 12 and adjust the same to the required. distance from the metallic tympan 14'. The bobbin 15 is mounted on the rounded end of said polar extension 13. Secured to the opposite pole-piece 12 by screws 17 is a metallic box 16, preferably of brass; but it may be formed ,of any other suitable material. The front part is turned, faced, and fitted with a screwed ring 18, which clamps the tympan 14'. A soft-iron screw 19, fitted with a screwed soft-iron, washer 14, passes through a tapped holein the pole-piece 12' and carries near its extremity a flbobbin 15, both bobbins being filled with insulated wire 22 of suitable size for producingtherequired effect, which is joined in sericsor'pan allel, passed through the insulated holes .23 in box 16, and connected for long distances to the secondary wire 22' of the inductioncoil 24; but for short distances it may be joined in series with .wire 00, leading from the microphone 5, or the microphone may be left out and they ends of the wires upon the inducing-bobbins joined, respectively, to line and earth. The back of the box 16 is formed or fitted with two elbows 25, which conduct the sound-waves set up by the tympan 14 to the ear by means of the flexible tubes 26, cone nected to the elbows 25 by ferrules 25",screwed into the plates 25", having trumpet ends 27. (See, also, Figs. 2 and 3.) When the telephone is not in use, the trumpet ends may be used to depress the fork of switch-lever 27 thereby putting the bell 37 to line. By lifting them out the bell is cutout and the telephone put to line in the usual manner.

The operation of my invention will be readily understood.

By reason of the compound ringing magnet formed as described I am able to concentrate a very powerful magnetic field upon the points of the soft-iron extensions 13 19 adjacent to the tympan, with the result that loud articulate speech is obtained as asimple telephone. One inducing-bobbin only may be used, in'which casethe extension-piece 19 has the etfect of polarizing the tympan-plate 14. It is to be understood that the rotation of the armaturell within the pole-pieces 9 by means of the disk 9 and handle 9 operating the same when used for ringing the hell, does not in any way interfere with the successful transmission or reception or speech.

The general external appearance of a telephone combination constructed as just described will be understood from the drawing shown in Fig. 3.

A variation of my invention consists in the employment of two distinct tympans inclosed within a metallic or other cylinder 16, both tympans being inductively acted upon by a T-shaped extension mounted upon one of the compound-magnet poles, the opposite pole being so constructed as to polarize them, (see Figs. 4, 5, 6, 7, 8, and 9,) wherein 1 is the lid of the case 1. Upon this may be mounted, byglueing, screwing, or otherwise, a square or round box 2, containing any eifective microphone 5, as seen bydotted lines, Fig. 5.

Secured to the case l by bolts 6 are the magnet-bars 8. The pole-pieces 9 are bored out to receive the Siemens or other armature 11 (see also Fig. 1) of the well-known type, which is employed for ringing the alternating bell, the armature being rotated by a disk 9, as shown, or any of the well-known means. The upper ends of the magnet-bars 8 are secured by screwing or riveting to the polepieces 12 12, one of which carries a T-shaped soft-iron extension 13, (see also Figs. 6 and 9,) the shank of which is of square section and passes through a corresponding hole formed in pole-piece 12', a screw being formed upon the extreme end, upon which a soft iron milled clamp nut 14" is threaded. Upon either side of the T-shaped extension 13 are inducing-bobbins 15 15, filled with insulated wire 22, which is joined in series or parallel, the ends passing out through the ebonite plug 23' to the secondary wire of induction-coil24 and earth and line terminals through the switch. The two ferrotype tympans 14' are each clamped by a screwed-ring 28 into a recess formed in the soft-iron cups 29, which are each fitted with a raised ring 30, milled on its edge. The outer ends are screwed into two rings 31, forming part of the soft-iron pole-piece 12, secured to the three magnetbars 8. These rings have the effect of polarizing the tympans 14'. Holes 32 are bored in the ends of each cup,.and into these are fitted the ferrules 25', screwed into plates 25", let into the woodwork of case. The ear-tubes 26 are fitted to the ferrules 25, the trumpet ends 27 being employed to depress the forked switch-lever 27, pivoted to bracket m" and T-shaped bar 34 when the telephone is out of use, as described already.

In some cases the tympans may be secured and adjusted 'by the modification shown in Fig. 7, wherein the cylinder 16 is screwed internally, and also the cup 29, engaging there with. The tympan 14' is packed with a metallic ring 28.

This instrument is well suited for use over long distances as a simple telephone, and when so used I prefer to mount the trumpet mouthpiece 2 upon the lid of case 1, (see Fig. 5,) ahole y being made inthe'cylinder 16, so that the sound-waves may act upon both tympans.

A further modification of my invention is shown in Fig. 8. In this case I mount upon the pole-pieces 12 12', secured to the bellmagnets 8, a shallow cylindrical metallic box 16, which is cored out internally and formed with two trumpet-shaped nozzles 25, to which the ear-tubes 26 are connected by ferrules 25, as previously described. Ascrewed recess 33 is formed in each side of box 16, and in these are placed the double tympans 14' which are held fastby the screwed rings 28. Each polepiece 12 12 carries a screwed soft-iron extension 13, fitted with soft-iron washer 14 and milled nut 14". The inner extremity of each extension carries inducing-bobbins 15 15, filled with wire, which may be coupled in series or parallel and connected to line and earth or to an induction-coil, as already described. Owing to the nicety with which the extensions 13 can beset and the closeness and strength of the magnetic field, this form of instrument is particularly suited for transmitting speech over long distances.

The switching-gear (shown in Figs. 1 and 4) is of the usual form employed with magnetotelephone combinations. When the eartrumpets 27 are in the forked ends of lever 27', the T-shaped bar 34, (see Figs. 1 and 4,) which is connected to one of the line and earth terminals 42 42, (see dotted lines, Fig. 4,) connects the two springs 36 36, thereby putting the bell 37, operated by magnet-coils 37' and hammer 37", and the armature 11 of the generator into circuit. When the trumpet ends 27 are lifted out, the springs 38, connected to bar, draws it upward and cuts out the bell and connects the three upper springs 39 40 41, thereby closing the circuit of local battery coupled up to terminals 35 35' through the microphone and primary of ind uction-coil by the hinges v and wires .10 0c and putting the telephone and secondary wire of inductioncoil to line.

I am aware that telephonic apparatus has been described in which the horseshoe magnets employed forringing or extensions or pole-pieces fitted thereto (either form carrying inducing-bobbins) are, in combination with a metallic tympan or a tympan formed of magnetic material, used for transmitting speech; but I do not broadly claim such a combination. Although for the purposes of description Ihave shown a microphone mounted up in connection with my invention, I do not claim the form shown; nor do I lay claim to the switching device described or the connections therefrom to the various parts of the instrument by themselves.

What I do claim isl. The combination of the compound ringing-magnets having soft-iron pole-pieces carried by one end with a tympan-box and tympan and adjustable polar extensions, each carrying an inducing-bobbin filled with a conducting-wire connecting line and earth, and the generator at the reverse end, operating substantially as described.

2. The combination of the compoundmagnets having at one end pole-pieces supporting the cylinder, the rings through which the said cylinder is supported by said pole-pieces, the

two tympan-plates carried by the said cylin- T-shaped extension 13, carrying inducingcoils, operating in the manner set forth.

Intestimony whereof I have set my hand in presence of two witnesses.

CHARLES STEWART FORBES.

Witnesses:

. FRANCIS M. ROGER,

21 Firzsbury Padt, London, E. C.

J. W. SHEPPARD,

Clerk to Messrs. Grain 6% Sorts, 46 Lombard Street, London, England. 

